18 Who against hope believed in hope, that he might become the father of many nations, according to that which was spoken, So shall thy seed be.

19 And being not weak in faith, he considered not his own body now dead, when he was about an hundred years old, neither yet the deadness of Sara’s womb:20 He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God;21 And being fully persuaded that, what he had promised, he was able also to perform.

Abraham did not know how he would become the father of nations, but he heard God’s promises to him. Even if he was 100 years old and his wife was beyond childbearing age, God gave him the ability to have a child. He did get side-tracked and tried to do things on his own and the way it could make sense to him. After making a mistake and doing things his way, God did things as he had promised. Many times we try to rush things and do things our way instead of waiting on God. Our response of faith is important to the outcome of the promises.